Loa loa (African eyeworm) is a filarial nematode estimated to infect 3-13 million people in central and western Africa, and is the causative agent for loiasis. Infected individuals may exhibit a range of relatively benign symptoms. However, those who are lifelong inhabitants of endemic areas are generally asymptomatic, even with the presence of large numbers of microfilariae circulating throughout their bloodstreams. Loiasis is, nevertheless, a public health concern due to the occurrence of greater than 1,000 severe adverse reactions (including fatal encephalopathies) in Loa-infected individuals receiving ivermectin as a result of mass drug administration (MDA) programs aimed at the elimination of onchocerciasis and lymphatic filariasis. Consequently, disruption of further MDA has occurred in certain communities where these diseases are co-endemic.
The mechanism of Loa-related post-ivermectin encephalopathy is unclear, but the risk appears to be greatest with patients having blood microfilariae (mf) counts greater than about >8000 mf/ml (for non-neurological adverse events) and >25000 mf/ml (for severe, neurological adverse events). Reducing or preventing disruption of MDA therefore requires that patients with high-levels of circulating L. loa microfilaremia be identified and excluded from treatment. Currently available methods for detecting Loa loa such as, for example, microscopic evaluation of blood samples, real time quantitative polymerase chain reaction (PCR)/real time (RT)-PCR, and loop-mediated isothermal amplification (LAMP) may require sophisticated instrumentation, which may be impractical for widespread screening. Accordingly, there exists a need for improved methods for detecting the presence of L. loa. 